Dr. Elizabeth Matsui, a pediatrician, is an associate professor at the Johns Hopkins University and a national expert on asthma who has spent 15 years studying the effects of indoor environments on children with the disease, particularly in Baltimore. She spoke with Michael Errigo of Capital News Service about what triggers asthma and how the rates of asthma are higher in low-income neighborhoods because those triggers are everywhere.
Q: Could you start with some background on asthma?
Matsui: It’s a disease in which there’s inflammation in the lungs. … It’s typically triggered by some sort of external insult. Of course your lungs are the first organ system after your nasal passages that interacts with the environment and so things that you breathe in can induce or trigger inflammation and then the inflammation leads to asthma symptoms.
Q: Is it similar to, say, an allergy to peanuts where I may be allergic and my sister might not be? Where certain people can live in the same environment and not get sick?
Matsui: Exactly.
Q: So then why would the rates of asthma be higher among poorer children?
Matsui: That’s not entirely well understood but part of it may be that if you have a genetic susceptibility to an environmental exposure and you live in that environment then you will have a manifestation of that disease.
So the prevalence of asthma in low-income Baltimore neighborhoods typically we think is about 25 to 30 percent – which, if you think about a pediatric population, is extraordinarily high. To give you a benchmark, the national prevalence of asthma in children is about 10 percent.
Q: What are the environmental triggers?
Matsui: There are a couple of concepts here. One is allergy. Probably many of you have experienced hay fever or spring time allergies. What happens is that your immune system has made an allergic antibody, and the antibody doesn’t cause any problems until pollen season and it recognizes the pollen and causes inflammation.
Those same kinds of things can happen in the lungs with an allergic response. There are allergens that are present year-round—perennial allergens—predominantly indoors. And if someone is allergic to those allergens and they’re inhaling them, then it can trigger this inflammatory response in the lungs and can lead to symptoms.
And then there’s another basket of exposures that’s related to irritants – things like gaseous pollutants, so nitrogen dioxide is one of them. Those can directly cause inflammation without needing to have the presence of an allergic antibody that recognizes them.
Q: Would you elaborate?
Matsui: For families that have a gas stoves and gas heat, those homes have higher levels of nitrogen dioxide.
For a family that maybe is having trouble heating their home and they run the oven or use the stove as a source of heat, there are higher levels of nitrogen dioxide. And that gets inhaled and causes inflammation. That’s the main gaseous pollutant that we’ve identified.
Then there are microscopic particles in the air inside homes that can trigger asthma inflammation. There are also larger particles called coarse particles. These things are also produced by vehicular traffic, so they can come indoors from outdoors. Here in Baltimore, the concentration of those pollutants is higher indoors than outdoors, among high poverty neighborhoods.
Q: Could you list some typical allergens and some typical pollutants?
Matsui: Of the typical allergens that are a problem in our community, the main one by far is mouse allergen. We detect it in 100 percent of homes and we have measured it in air samples in about 85 to 90 percent of bedrooms among the children who have participated in our studies.
That is the No. 1 public health environmental contributor to asthma ER visits in Baltimore.
The mouse allergen is concentrated in the urine. It’s airborne because it’s carried on very small, very light particles so it’s airborne for a long time and then it sticks to things – clothes, walls. Other animal allergens are similar.
The key thing for getting rid of mice is identifying all the holes and cracks through which they can enter, and they can enter the home through holes as small as the diameter of a pencil. Those holes have to be sealed up and typically the best thing is a copper mesh and a foam filler. Repeatedly setting traps, storing all food in containers that can’t be chewed through, having restricted areas of the home for eating so there are no crumbs, cleaning all counters, floors, dishes after eating. These are the sort of things that we talk to families about.
Q: If you’re removed from the environment once the disease is established, what happens?
Matsui: There are some very old studies that are not applicable to the Baltimore population. People used to, decades ago, if they had dust mite allergy and had dust mite-driven asthma, they would go to the mountains in Switzerland, high up in the elevation where the climate was arid and there were very few dust mites and their asthma would get better. So that was the first observation a long time ago about what happens when you change environments.
There are not really studies yet looking at the effects of if someone moves from poor housing in a high-poverty neighborhood to better housing in a low-poverty neighborhood, what happens to the exposures and what happens to asthma. We have a study we’re doing now to actually answer that exact question. We’re enrolling kids and following them from before they move until after they move.
Questions and answers have been edited for length and clarity.